Power train for a utility vehicle

ABSTRACT

A power train for a vehicle includes a gearbox with an input shaft and an output shaft and is configured such that the input shaft drives the output shaft at a single speed ratio in a first direction and a single speed ratio in a second direction. The output shaft is coupleable with the front and rear vehicle axles to separately drive each axle. Further, a continuously variable transmission is connected with an engine shaft and with the gearbox input shaft such that the engine shaft drives the input shaft within a range of speed ratios from less than 1 to greater than 3. Front and rear differentials are coupled with each axle and with the output shaft and drive the axles at different speed ratios such that a base surface drives the front axle independently of the front differential when at least one rear wheel rolls upon the surface.

This application is a divisional of U.S. application Ser. No.10/983,496, filed Nov. 8, 2004, now U.S. Pat. No. 7,377,351, whichclaims priority to U.S. Provisional Application Ser. No. 60/518,539,filed Nov. 7, 2003, the entire contents of which are incorporated hereinby reference.

BACKGROUND OF THE INVENTION

The present invention relates to vehicles such as utility vehicles, golfcars and NEVS, and more particularly to power trains for such vehicles.

Vehicles such as utility vehicles, golf cars, NEVs, etc., typicallyinclude a frame, front and rear axles connected with the frame, twowheels connected with each axle and an engine or a motor mounted on theframe and configured to rotatably drive at least one axle. When the“prime mover” is an engine, such vehicles generally include a powertrain for transferring engine power from an output shaft of the engineto the driven axle or axles. As an engine output shaft generally rotatesat a much higher speed than the desired rotational speed of the drivenaxle(s), power trains typically include a transmission that functions todrive the axles at a significantly lesser speed than the speed of engineoutput shaft. Often, power trains include one or two rotatable propellershafts that function to transfer torque and rotational motion from thetransmission to the one or more driven axles.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a power train for a vehiclehaving a frame, an engine mounted to the frame and having a rotatableoutput shaft, and front and rear axles each rotatably connected with theframe. The power train basically comprises a gearbox including arotatable input shaft and a rotatable output shaft operably coupleablewith the input shaft. The gear box is configured such that the inputshaft drives the output shaft at a single, fixed speed ratio in a firstrotational direction and alternatively drives the output shaft at asingle, fixed speed ratio in a second, opposing rotational direction.The output shaft is operatively coupleable with the front axle and withthe rear axle so as to separately drive each one of the two axles torotate with respect to the frame. Further, a continuously variabletransmission unit is connected with the engine shaft and with thegearbox input shaft such that the engine shaft drives the input shaft.The transmission unit is configured so that a ratio of the engine shaftrotational speed to the input shaft rotational speed is variable withina range of values having a lower limit of less than 1 and an upper limitof greater than 3.

In another aspect, the present invention is also a power train for avehicle having a frame, an engine mounted to the frame and having arotatable output shaft, and front and rear axles each rotatablyconnected with the frame. Each axle includes two axle shafts and twowheels, each wheel being connected with a separate one of the axleshafts and rollable upon a base surface. The power train comprises atransmission operably connected with the engine and having an outputshaft. A first propeller shaft has a first end, the first end beingconnected with the transmission output shaft, and a second end. A frontdifferential is connected with each one of the two front axle shafts andhas a gear member configured to rotatably drive the two front shafts.The front differential is operatively connected with the second end ofthe first propeller shaft such that the first propeller shaft drives thegear member at a first speed reduction ratio. Further, a secondpropeller shaft has a first end, the first end being connected with thetransmission output shaft, and a second end. A rear differential isconnected with each one of the two rear axle shafts and having a gearmember configured to rotatably drive the two rear shafts. The reardifferential is operatively connected with the second end of the secondpropeller shaft such that the second propeller shaft drives the reardifferential gear member at a second speed reduction ratio. The firstspeed ratio is greater than the second speed ratio such that the basesurface drives the two front axle shafts to rotate independently of thefront differential gear member when at least one of the two rear wheelsrolls upon the base surface. Furthermore, the rear differential isconfigured to releasably connect each one of the two rear axle shaftswith the other one of the two rear axle shafts when each of the two rearwheels rolls at about the same speed as the other one of the two rearwheels such that the two rear axle shafts rotate generally as a singleunit. The rear differential is also configured to alternativelydisconnect at least one of the two rear axle shafts from the other oneof the two rear axle shafts when one of the two rear wheels rolls at agreater speed than the other one of the two rear wheels during a turningmovement of the vehicle.

In a further aspect, the present invention is a transmission for avehicle that includes a frame, an engine connected with the frame andhaving an output shaft rotatable about a central axis, front and rearaxles rotatably connected with the frame, and two propeller shafts eachconnected with a separate one of the two axles. The transmissioncomprises an input shaft rotatable about a central axis extendingthrough the input shaft. The input shaft is operably coupleable with theengine shaft such that the engine shaft drives the input shaft to rotateabout the input shaft central axis, the input shaft axis extendinggenerally parallel with respect to the engine shaft axis. Further, anoutput shaft is rotatable about a central axis extending through theoutput shaft and is connected with each one of the two propeller shafts.The output shaft is operably coupleable with the input shaft such thatthe input shaft drives the output shaft to rotate about the output shaftcentral axis, the output shaft axis extending generally parallel withrespect to the input shaft axis.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the detailed description of thepreferred embodiments of the present invention, will be betterunderstood when read in conjunction with the appended drawings. For thepurpose of illustrating the invention, there is shown in the drawings,which are diagrammatic, embodiments that are presently preferred. Itshould be understood, however, that the present invention is not limitedto the precise arrangements and instrumentalities shown. In thedrawings:

FIG. 1 is a perspective view of a utility vehicle incorporating a powertrain in accordance with the present invention;

FIG. 2 is a top plan view of the power train, shown mounted to a frameof the vehicle;

FIG. 3 is another top plan view of the power train, shown separated fromthe frame;

FIG. 4 is a perspective view of a transmission of the power train, shownconnected with the engine;

FIG. 5 is a top plan view of the transmission and engine;

FIG. 6 is an exploded view of a first or “drive” pulley of thetransmission;

FIG. 7 is an exploded view of a second or “driven” pulley of thetransmission;

FIG. 8 is an exploded view of a gearbox of the transmission;

FIG. 9 is a cross-sectional view of the gearbox;

FIG. 10 is a perspective view of the components of the gearbox, shownseparated from a housing of the gearbox;

FIG. 11 is an exploded view of an input shaft of the gearbox;

FIG. 12 is an exploded view of an output shaft of the gearbox;

FIG. 13 is an exploded view of an intermediate shaft of the gearbox;

FIG. 14 is an exploded view of a front differential of the power train;

FIG. 15 is an enlarged, axial cross-sectional view of the frontdifferential;

FIGS. 16A and 16B, collectively FIG. 16, are two radial cross-sectionalviews through line 16-16 of FIG. 15, each showing a different relativeposition of a carrier and a side member;

FIG. 17 is an exploded view of a rear differential of the power train;

FIG. 18 is an enlarged, perspective view of a carrier, a carrier housingand a gear member of the rear differential;

FIG. 19 is a greatly enlarged, partly broken-away side plan view of therear differential carrier;

FIG. 20 is a greatly enlarged cross-sectional view of the reardifferential carrier; and

FIG. 21 is an even more greatly enlarged view of a broken-away portionof FIG. 20, as indicated by arrow 21.

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, left”, “lower”, “upper”,“upward”, “down” and “downward” designate directions in the drawings towhich reference is made. The words “inner”, “inwardly” and “outer”,“outwardly” refer to directions toward and away from, respectively, adesignated centerline or a geometric center of an element beingdescribed, the particular meaning being readily apparent from thecontext of the description. Further, as used herein, the word“connected” is intended to include direct connections between twomembers without any other members interposed therebetween and indirectconnections between members in which one or more other members areinterposed therebetween. The terminology includes the words specificallymentioned above, derivatives thereof, and words or similar import.

Referring now to the drawings in detail, wherein like numbers are usedto indicate like elements throughout, there is shown in FIGS. 1-21 apower train 10 for a utility vehicle 1. The vehicle 1 preferablyincludes a frame 2 with a centerline 2 a, an engine 3 with a rotatableoutput shaft 4, and front and rear axles 5 and 6 rotatably connectedwith the frame 2, with each axle 5, 6 preferably including two axleshafts 7A, 7B and 8A, 8B, respectively, and two wheels 9A, 9B and 9C, 9Deach connected with a separate one of the axle shafts 7A, 7B, 8A, 8B,respectively, and rollable upon a base or ground surface G. The powertrain 10 basically comprises a transmission 12 operably connected withthe engine 3 and having an output shaft 13, first and second propellershafts 14, 16, respectively, each operably connected with transmissionoutput shaft 13, a front differential 18 connected with the firstpropeller shaft 14 and operatively connected with the front axle 5, anda rear differential 20 connected with the second propeller shaft 16 andoperatively connected with the rear axle 6. The transmission 12preferably comprises two main components; a continuously variabletransmission unit 22 (a “CVT” or “CV” transmission) and a gearbox or“transfer case” 24 operably connected with the transmission unit 22. Thegearbox 24 includes an input shaft 26 rotatable about a central axis 27and an output shaft 28 rotatable about a central axis 29 and operablycoupleable with the input shaft 26, the gearbox output shaft 28providing the transmission output shaft 13.

Preferably, the gear box 24 is configured such that the input shaft 26rotatably drives the output shaft 28 at a single, fixed speed ratio in afirst rotational direction d_(R1) and alternatively drives the outputshaft 28 at a single, fixed speed ratio in a second, opposing rotationaldirection d_(R2), as described below. Further, the CV transmission unit22 is connected with the engine output shaft 4 and with the gearboxinput shaft 26 such that the engine output shaft 4 rotatably drives theinput shaft 26 through the CV transmission unit 22. The transmissionunit 22 is preferably configured so that a ratio R_(T) of the engineshaft rotational speed S_(E) to the input shaft rotational speed S_(I)(i.e., R_(T)=S_(E)/S_(T)) is variable within a range of values having alower limit of less than 1 and an upper limit of greater than 3. Mostpreferably, the speed ratio lower limit is about 0.6 and the speed ratioupper limit is about 3.6. As such, the gearbox output shaft 28 isrotatable at a highest speed setting when the transmission unit speedratio is about 0.6 and rotatable at a lowest speed setting when thetransmission unit speed ratio is about 3.6, the highest speed settingbeing greater than the lowest speed setting by about a factor of 6.Further, the transmission 12 is preferably configured such that theinput shaft axis 27 extends generally parallel with respect to theengine shaft axis 4 a and the output shaft axis 29 extends generallyparallel with respect to the input shaft axis 27, with each axis 4 a, 27and 29 preferably extending generally parallel with respect to the framecenterline 2 a, for reasons discussed below.

The first propeller shaft 14 preferably has a first end 14 a connectedwith the gearbox output shaft 28, a second end 14 b and a central axis15 extending between the two ends 14 a, 14 b. The front differential 18is connected with each one of the two front axle shafts 7A, 7B and has agear member 30 (e.g., FIG. 14) configured to rotatably drive the twofront axle shafts 7A, 7B to rotate about a front axle axis 31. Further,the front differential 18 is operatively connected with the second end14 b of the first propeller shaft 14 such that the first propeller shaft14 drives the gear member 30 at a first speed reduction ratio R₁. Inaddition, the second propeller shaft 16 preferably has a first end 16 a,the first end 16 a being connected with the gearbox output shaft 28, asecond end 16 b and a central axis 17 extending between the two ends 16a, 16 b. The rear differential 20 is connected with each one of the tworear axle shafts 8A, 8B and has a gear member 32 (e.g., FIG. 17)configured to rotatably drive the two rear axle shafts 8A, 8B to rotateabout a rear axle axis 33. Further, the rear differential 20 isoperatively connected with the second end 16 b of the second propellershaft 16 such that the second propeller shaft 16 drives the gear member32 at a second speed reduction ratio R₂.

Each propeller shaft 14, 16 is driven by the output shaft 28 such thateach propeller shaft 14, 16 rotates about the respective shaft axis 15,17 at about the same rotational speed as the other propeller shaft 16,14. However, the first speed ratio R₁ is greater than the second speedratio R₂ such that the front differential 18 rotatably drives the frontaxle shafts 7A, 7B at a speed S_(F) that is lesser or “slower” than thespeed S_(R) at which the rear differential drives the rear axle shafts8A, 8B. As such, the rear wheels 9C, 9D drive the vehicle 1 and causethe base surface G to drive the front wheels 9A, 9B to roll at about thesame speed as the rear wheels 9C, 9D. As such, the two front axle shafts7A, 7B connected to the front wheels 9A, 9B rotate at speed greater thanthe rotational speed of the front differential gear member 30, such thatno torque is transferred from the first propeller shaft 14 to the frontaxle shafts 7A, 7B. Thus, the base surface G drives the two front axleshafts 7A, 7B to rotate at a greater speed than the front differentialgear member 30 when at least one of the two rear wheels 9C, 9D rollsupon the base surface G. When both rear wheels 9C, 9D slip such that thefront wheels 9A, 9B begin to slow down (i.e., rotate at a lesser speed),the front differential 18 is configured to operatively couple the gearmember 30 with the two front axle shaft 7A, 7B such that the firstpropeller shaft 14 rotatably drives the axle shafts 7A, 7B, as discussedin greater detail below.

Preferably, the front differential 18 and the rear differential 20 areeach configured to releasably connect the two associated axle shafts 7A,7B or 8A, 8B, respectively, when the vehicle 1 is traveling generally ina straight line and to disconnect at least one of the axle shafts 7A, 7Bor 8A, 8B from the associated shaft 7B, 7A or 8B, 8A when the vehicle 1performs a turning or steering movement. More specifically, the frontdifferential 18 is configured to releasably connect each one of the twofront axle shafts 7A, 7B with the other one of the two front axle shafts7B, 7A when each of the two front wheels 9A, 9B rolls at about the samespeed as the other one of the two front wheels 9B, 9A, such that the twofront axle shafts 7A, 7B rotate generally as a single unit (i.e., rotateas a connected-together assembly). The front differential 18 is furtherconfigured to alternatively disconnect at least one of the two frontaxle shafts 7A, 7B from the other one of the two front axle shafts 7B,7A when one of the two front wheels 9A, 9B rolls at a greater speed thanthe other one of the two front wheels 9B, 9A during a turning movementof the vehicle 1. Further, the rear differential 20 is configured toreleasably connect each one of the two rear axle shafts 8A, 8B with theother one of the two rear axle shafts 8B, 8A when each of the two rearwheels 9C, 9D rolls at about the same speed as the other one of the tworear wheels 9D, 9C such that the two rear axle shafts 8A, 8B rotategenerally as a single unit. The rear differential 20 is furtherconfigured to alternatively disconnect at least one of the two rear axleshafts 8A, 8B from the other one of the two rear axle shafts 8B, 8A whenone of the two rear wheels 9C, 9D rolls at a greater speed than theother one of the two rear wheels 9D, 9C during a turning movement of thevehicle 1. As such, both the front and rear differentials 18 and 20function to generally maintain the associated axle shafts 7A, 7B and 8A,8B connected together, so that in the event that one wheel 9A, 9B or 9C,9D slips, the other wheel 9B, 9A or 9D, 9C receives all the torque fromthe associated propeller shaft 14, 16, respectively, but also permitsthe “outer” wheel 9A, 9B and/or 9C, 9D to roll faster than theassociated “inner” wheel 9B, 9A or/and 9D, 9C during vehicle turning.

With the structure above, the power train 10 of the present inventionenables the vehicle 1 to function in all-wheel drive and through arelatively substantial range of speeds, preferably from zero miles perhour (0 mph) through at least twenty-five (25) mph, and to operate thevehicle generally without loss of traction, without the necessity of theoperator performing any shifting, axle-locking or other such controloperation. Having described the basic elements and structure of thepower train 10 of the present invention, each of these and othercomponents are described in detail below.

Referring first to FIGS. 1 and 2, the power train 10 is preferably usedwith a vehicle 1 that is generally sized so as to operate as a utilityvehicle for use in golf courses, factories, parks, etc., or for use as aneighborhood utility vehicle (“NEV”) for travelling relatively shortdistances from a home. However, the basic structure of the power train10 and all novel components thereof may be used in any other appropriateapplication, such as in generally larger sized automobiles, trucks, etc.

Preferably, the frame 2 has a longitudinal centerline 2 a and ispreferably constructed as a generally rectangular truss formed of aplurality of bars or beams, but may be formed in any appropriate manner.The engine 3 is preferably located generally centrally on the frame 2 soas to be spaced longitudinally from each of the front and rear axles 5,6, respectively, and is oriented such that the axis 4 a of the engineoutput shaft 4 extends generally parallel with respect to the framecenterline, and thus generally perpendicular to each axle 5, 6. Further,the engine 3 is preferably a standard internal combustion engine, mostpreferably fueled by gasoline or diesel fuel, but the power train 10 mayalternatively be used with any other type of engine, such as forexample, a fuel cell engine or a gas-electric hybrid engine. The scopeof the present invention embraces these and all other appropriateapplications of the power train 10.

Referring now to FIGS. 4-7, the CV transmission unit 22 is preferably a“belt drive” type of transmission and is configured to automaticallyincrease the speed ratio R_(T) (S_(E)/S_(I)) when the engine shaft speedS_(E) increases and to decrease the speed ratio R_(T) when torque on theinput shaft 26 increases. Preferably, the CV transmission unit 22basically includes a drive pulley 36 mounted on the engine shaft 4, adriven pulley 38 mounted on the gearbox input shaft 26 and a continuousflexible element 40 driveably engaging the drive and driven pulleys 36,38, respectively, each being described in detail below. Although a belttype of drive is preferred, the CV transmission unit 22 may be any otherappropriate type of CV transmission, such as for example a disk andwheel unit, a cone and wheel device, a toroidal CVT, a planetary gearset and gyroscope unit, a ratchet CVT, etc. In addition, the power train10 may include a transmission unit 22 that is a “non-continuously”variable transmission, such as a spur, bevel and/or planetary gear trainor a non-variable belt drive, although such an arrangement would notprovide certain desired features of the present invention as describedherein.

Referring to FIGS. 4, 5 and 6, the drive pulley 36 is connected with theengine shaft 3 a and has a variable effective diameter D_(E1) (FIG. 5)or “pitch diameter”, i.e., the diameter at which the flexible element 40is driven so as to establish the tangential velocity at an effectivediameter D_(E2) (FIG. 5) of the driven pulley 38, as discussed below.The drive pulley 36 is configured such that the pulley effectivediameter D_(E1) increases when engine shaft speed S_(E) increases andthe effective diameter D_(E1) decreases when torque on the input shaft26 increases. Preferably, the drive pulley 36 includes first and secondsheaves 42, 44 disposed on the engine shaft 4 and a biasing member 46configured to bias the second sheave 44 generally away from the firstsheave 42. More specifically, each drive pulley sheave 42, 44 ispreferably formed as a generally annular disk with a frustaconicalportion providing a tapered working surface 43, 45, respectively. Thetwo sheaves 42, 44 are arranged with respect to each other such that thetwo working surfaces 43, 45 are generally facing, the flexible element40 being generally “sandwiched” between facing annular sections (notindicated) of the two surfaces 43, 45 that are spaced apart by about thewidth W_(B) (FIG. 4) of the element 40. With this structure, the drivepulley effective diameter D_(E1) is varied or adjusted by the varyingthe axial spacing distance d_(S1) between the two sheaves 42, 44. Inother words, when the spacing distance d_(S1) increases (i.e., thesheaves 42, 44 move apart), the flexible element 40 slidesradially-inwardly along the tapered working surface 43, 45, therebydecreasing the effective diameter D_(E1). Conversely, when the spacingdistance d_(S1) decreases (i.e., the sheaves 42, 44 move toward eachother), the flexible element 40 is pushed radially outwardly along thetapered working surfaces 43, 45 so as to increase the effective diameterD_(E1).

Referring particularly to FIGS. 4 and 6, the first sheave 42 ispreferably formed as to further include a central stub shaft 42 a andthe second sheave 44 is preferably slidably disposed on the shaft 42 a.The drive pulley 36 also preferably includes a first retainer member 47connected with the outer end of the stub shaft 42 a and a secondretainer member 49 attached to the second sheave 44 and spaced axiallyfrom the first member 47. The biasing member 46, which is preferably acoil spring, extends between the two retainer members 47, 49 and isconfigured to bias the second member 49 generally away from the firstmember 47, and thereby bias the second sheave 44 generally away from thefirst sheave 42. Further, a pair of weighted levers 51 are pivotallyattached to the second sheave 44 and are contactable with the firstretainer member 47.

With this structure, when the engine shaft 4 rotates at a sufficientlyhigh speed S_(E), centrifugal force causes the weighted levers 51 topivot radially outwardly from the axis 4 a and push against the firstretainer member 47 (fixed to the first sheave 42). Such movement of theweighted levers 51 causes the second sheave 44 (and second retainermember 49) to slidably displace on the stub shaft 42 a toward the firstsheave 42, against the biasing force of the biasing member 46, so as tothereby increase the drive pulley effective diameter D_(E1). When theengine output shaft 4 rotates at a lesser or slower speed, the weightedlevers 51 pivot inwardly toward the shaft axis 4 a, enabling the biasingmember 46 to push the second retainer member 49 to displace generallyaway from the first retainer member 47. During such displacement, thesecond member 49 “carries” the second sheave 44 to slidably displace onthe stub shaft 42 a away from the first sheave 42, thereby decreasingthe drive pulley effective diameter D_(E1).

Referring to FIGS. 4, 5 and 7, the driven pulley 38 is connected withthe gearbox input shaft 26 and has a variable effective diameter D_(E2)(FIG. 5). The driven pulley 38 is configured such that the driven pulleyeffective diameter D_(E2) increases when the drive pulley effectivediameter D_(E1) decreases and decreases when the drive pulley effectivediameter D_(E1) increases, as discussed in further detail below.Preferably, the driven pulley 38 includes first and second sheaves 48,50 disposed on the input shaft 26 and a biasing member 52 configured tobias the second sheave 50 generally toward the first sheave 48. Morespecifically, each driven pulley sheave 48, 50 is preferably formed in agenerally similar manner as the two drive pulley sheaves 42, 44, i.e.,as a generally annular disk with a frustaconical portion providing atapered working surface 53, 55, respectively.

As with the drive pulley 36, the driven pulley effective diameter D_(E2)is varied or adjusted by the varying the axial spacing distance d_(S2)between the two sheaves 48, 50. Specifically, when the spacing distanced_(s2) increases, the flexible element 40 slides radially-inwardly alongthe tapered working surfaces 53 and 55 such that the pulley effectivediameter D_(E2) decreases. Alternatively, when the spacing distanced_(s2) decreases, the flexible element 40 is pushed radially outwardlyalong the tapered working surfaces 53 and 55 such that the effectivediameter D_(E2) increases. Preferably, the first sheave 48 is formed soas to further include a central stub shaft 48 a, with the second sheave50 being slidably disposed on the shaft 48 a, and the biasing member 52is preferably a coil spring. The driven pulley 38 preferably furtherincludes a retainer member 57 connected with the free end of the stubshaft 48 a, the biasing member 52 being disposed on the shaft 48 a so asto extend between the second sheave 50 and the retainer member 57. Withthis structure, the biasing member 52 generally biases or pushes thesecond sheave 50 away from the retainer member 57, and thus generallytoward the first sheave 48.

Furthermore, the two sheaves 42, 44 of the drive pulley 36 and the twosheaves 48, 50 of the driven pulley 38 are relatively sized such thatthe CV transmission unit 22 is able to achieve engine speed-to-inputshaft speed ratios R_(T) in the range of less than 1 and greater then 3,and most preferably about 0.6 to about 3.6, as discussed above. As such,each one of the two driven pulley sheaves 48 and 50 is sized generallysubstantially larger than each of the two drive pulley sheaves 42 and44.

Referring to FIGS. 3 and 4, the flexible continuous element 40 isdisposed about each of the two pulleys 36 and 38 so as to operativelycouple the engine shaft 4 with the gearbox input shaft 26. The flexibleelement 40 has a generally fixed circumferential length (not indicated)and is preferably formed as a conventional belt 41, most preferably as apolymeric V-belt, but may alternatively be constructed as any otherappropriate flexible continuous mechanical elements, such as forexample, a flat belt, a chain, etc. The belt 41 basically functions totransmit torque from the engine shaft 4 to the gearbox input shaft 26such that the engine shaft rotatably drives the input shaft 26, eitherat a speed reduction (speed ratio R_(T)>1) or at an speed increase or“overdrive” condition (speed ratio R_(T)<1). Due to the fixed length ofthe belt 41, when the drive pulley effective diameter D_(E1) increaseswith increasing engine shaft speed S_(E), the portion of the belt 41disposed about the drive pulley 36 also increases, reducing the amountof belt length available to the driven pulley 38. Such “take-up” of agreater portion of the belt length by the drive pulley 36 pulls the belt41 radially inwardly on the driven pulley 38, causing the belt 41 to“wedge-apart” the two driven pulley sheaves 48, 50. In other words, thebelt 41 acts upon the driven pulley 38 such that the driven pulleysecond sheave 50 displaces generally away from the driven pulley firstsheave 48, against the biasing action of the biasing member 52, so as todecrease the effective diameter D_(E2) of the driven pulley 38 andthereby increase the transmission speed ratio R_(T). When the engineshaft speed S_(E) decreases such that the drive pulley effectivediameter D_(E1) decreases, the belt 41 slackens about the driven pulley38, permitting the biasing member 52 to displace the second sheave 48towards the first sheave 50, increasing the second pulley effectivediameter D_(E2) and reducing the transmission speed ratio R_(T). Thus,the CV transmission unit 22 is configured such that the transmissionspeed ratio R_(T) automatically decreases when the rotational speedS_(E) of the engine shaft 4 increases, such that gearbox input andoutput shafts 26 and 28 rotate at a greater or higher speed S₁, and thespeed ratio R_(T) automatically increases when engine shaft rotationalspeed S_(E) decreases, such that two gearbox shafts 26, 28 rotate at alesser or lower speed S₁.

Further, when torque load on the input shaft 26 increases, such as whenthe vehicle 1 begins to move up a sloped surface, a greater amount oftorque is required from the engine shaft 4 to rotate the input shaft 26,which increases the tension in the belt 41. The increased tension in thebelt 41 and resistance to rotation by the input shaft 26 causes the belt41 be pulled radially inwardly against the drive pulley 36 toward theengine shaft 4. As such, the belt 41 wedges between the two drive pulleysheaves 42, 44, which forces the movable or slidable sheave 44 todisplace away from the fixed sheave 42, thereby decreasing the drivepulley effective diameter D_(E1). As the amount of belt length about thedrive pulley decreases, the belt 41 slackens about the driven pulley 38such that the driven pulley biasing member 52 pushes the movable secondsheave 50 toward the fixed first sheave 48, increasing the effectivediameter D_(E2) until the slack is taken up by the two sheaves 48, 50.Thus, the transmission speed ratio R_(T) increases automatically whentorque on the input shaft 26 increases, thereby causing the gearboxinput and output shafts 26, 28 to be driven at a lesser or lower speed.

Referring to FIGS. 2-5 and 8-13, the gearbox 24 is preferably locatedgenerally centrally on the vehicle frame 2 so as to be spaced laterallyfrom the engine 3 and longitudinally from each of the two axles 5, 6. Asmentioned above, the gearbox 24 is preferably oriented on the frame 2such that the input shaft axis 27 and the output shaft axis 29 eachextend generally parallel with respect to the engine shaft axis 4 a, andgenerally parallel with respect to the frame centerline 2 a. Such anarrangement of the transmission 12 and the engine 3 permits the vehicle1 to utilize an engine 3 that is configured as an inline engine, as wellas typical V-twin engines and other types of engines, and eliminates any90° bevel gear arrangements typically required when an engine shaftextends perpendicularly with respect to a transmission output shaft.

Preferably, the gear box 24 further includes a housing 60 configured topartially contain the input shaft 26 and the output shaft 28, and othercomponents of the gear box 24 as described below. The gearbox housing 60also functions to relatively position the input and output shafts 26,28, such that the two shaft axes 27, 29 are generally parallel with eachother and the input shaft 26 is spaced generally above the output shaft28, and to rotatably support the two shafts 26, 28. Preferably, thehousing 60 has an exterior surface 60 a and an interior surface 60 bbounding an interior chamber C_(H), with each one of the input shaft 26and the output shaft 28 being partially disposed within the interiorchamber C_(H) and extending outwardly from the exterior surface 60 a.Preferably, the housing 60 also includes an upper, first opening 62 anda pair of aligned second openings 64A, 64B, each opening 62, 64A and 64Bextending between the exterior surface 60 a and the interior chamberC_(H). The input shaft 26 extends through the housing first opening 62such that a connective section 26 a of the shaft 26 is disposedexternally of the housing 60 and a gear-mounting section 26 b isdisposed within the housing chamber C_(H). Alternatively, the inputshaft 26 may be formed relatively axially longer so as to include asecond connective section (not shown) extending through the other firstopening 64B, such that a power take-off device (not shown) may beoperably coupled with the second connective section. Further, the outputshaft 28 extends through both second openings 64A and 64B such that twoconnective sections 28 a, 28 c extend from opposing sides of the housing60 and a central, gear-mounting section 28 b is disposed within thechamber C_(H). Preferably, the two shafts 26, 28 are rotatably connectedwith the housing 60 by two pairs of bearings 66, three bearings 66 beingdisposed adjacent to a separate one of three housing openings 62, 64Aand 64B and a fourth bearing 66 being generally aligned with the bearing66 adjacent to the first opening 62.

Furthermore, the gearbox housing 60 is preferably formed of twogenerally ovular-shaped shell halves 61A, 61B releasably connectedtogether by a plurality of threaded fasteners (not indicated) so as toform a generally rectangular box. Preferably, each shell half 61A, 61Bincludes three annular wall sections 63 extending from the housinginterior surface 60 b into the interior chamber C_(H), two wall sections63 on the first half 61A extending circumferentially at least partiallyabout the shaft openings 62 and 64A and one wall section 63 on thesecond shell half 61B extending circumferentially at least partiallyabout the shaft opening 64B. Each annular wall section 63 is sized toreceive a separate one of the bearings 66 so as thereby connect thebearing 66 with the housing 60. Although preferably formed as describedabove, the housing 60 may be formed in any other appropriate manner,such as being constructed of three or more shell portions or wallmembers, and/or may have any other appropriate shape, such as generallysquare, spherical or hemispherical.

Referring to FIGS. 8-12, the input shaft 26 is preferably formed as agenerally solid, generally circular bar 65 through which the input shaftaxis 27 longitudinally extends. The bar 65 has an enlarged centralportion 65 a and first and second end portions 65 b, 65 c extendingaxially from the central portion 65 a. The first end portion 65 b ispreferably sized relatively axially longer than the second end portion65 c and includes a plurality of axially extending splines 59 configuredto engage with the driven pulley 38, so as to form the input shaftconnective portion 26 a. Further, the output shaft 28 is preferablyformed as a generally solid, generally circular bar 67 through which theoutput axis 29 extends longitudinally. The bar 67 has an enlargedcentral portion 67 a and first and second end portions 67 b, 67 cextending axially from the central portion 67 a. Each output shaft endportion 67 b, 67 c includes a first, outer set of radially-outwardlyextending axial splines 68A, 68B, respectively, configured to engagewith one of the two propeller shafts 14, 16, as discussed below, so asto form the two connective portions 28 a, 28 c, and a second, inner setof radially-outwardly extending axial splines 69A, 69B configured toengage with a gear 82 and a sprocket 92, respectively, as discussedbelow.

Referring to FIGS. 8-10 and 13, the gearbox 24 further includes anintermediate shaft 70 disposed within the housing 60 generally betweenthe input shaft 26 and the output shaft 28. The intermediate shaft 70 isrotatably connected with the housing 60 by another pair of bearings 66disposed within a central pair of aligned wall sections 63, so as to berotatable about a third axis 71 extending generally parallel withrespect to the first and third axes 27, 29. Further, the intermediateshaft 70 is operably coupled with the input shaft 26 and is operativelycoupleable with the output shaft 28, such that the input shaft 26rotatably drives the output shaft 28 through the intermediate shaft 70.Preferably, the intermediate shaft 70 is formed as a generally solid,generally circular bar 72 through which the third axis 71 extendslongitudinally. As best shown in FIG. 13, the bar 72 has an enlargedcentral portion 72 a and first and second end portions 72 b, 72 cextending axially from the central portion 72 a. The central portion 72a includes a plurality of radially-outwardly extending axial splines 73and forms a coupler hub 74 configured to rotatably couple a dog clutch96 with the intermediate shaft 70, as discussed below. Further, thefirst end portion 72 b includes a set of radially-outwardly extendingaxial splines 76 configured to engage with a spur gear 84, as discussedin further detail below.

Referring now to FIGS. 8-13, the gearbox 24 preferably includes a geartrain 25 formed primarily of four spur gears 80, 82, 84 and 86 and twosprockets 90, 92 and configured to transmit rotational movement of theinput shaft 26 in a single angular or rotational direction A₁ torotation of the output shaft 28 in either of the two opposing rotationaldirections A₁ or A₂ (see FIG. 10). The gear train 25 includes a firstspur gear 80 fixedly disposed on the input shaft 26 and a second spurgear 82 fixedly disposed on the output shaft 28. A third spur gear 84 isfixedly disposed on the intermediate shaft 70 and is engaged with thefirst gear 80 on the input shaft 26. Further, a fourth spur gear 86 isrotatably disposed on the intermediate shaft 70 and is engaged with thesecond gear 82 on the output shaft 28. The fourth gear 86 has a hubportion 86 a with a set of radially-outwardly extending axial splines 87engageable with the dog clutch 96, as discussed below, so as toreleasably connect or couple the gear 86 with the shaft 70.

With this gear train structure, the input shaft 26 drives the outputshaft 28 to rotate in the first angular or rotational direction A₁ inthe following manner. The first gear 80 rotates at the speed S_(I) ofthe input shaft 26 (i.e., as effected by the CV unit 22) and rotatablydrives the third gear 84 on the intermediate shaft 70, causing theintermediate shaft 70 to rotate in the opposing, second rotationaldirection A₂ and at an intermediate speed S_(S) as reduced by a firstgear reduction G₁. Such rotation of the intermediate shaft 70 causes thefourth gear 86, when coupled with the shaft 70, to rotatably drive thesecond gear 82 on the output shaft 28, such that output shaft 28 rotatesin the first rotational direction A₁ at a “forward” output speed S_(F)as reduced by a second gear reduction G₂. Most preferably, the outputshaft 28 is preferably driven by the input shaft 26 in the first or“forward” rotational direction A₁ at a total gear reduction ratio G_(TF)of about four point nine eight (4.98).

However, the four gears 80, 82, 84 and 86 may alternatively beconfigured to provide any appropriate, desired gear ratio. Further, thegearbox 24 may alternatively include a second intermediate shaft (notshown) disposed between the input and intermediate shafts 26, 70 or theintermediate and output shafts 70, 28, and/or may include other types ofgears, such as worm gears, planetary gears, etc., either in combinationwith or in place of the spur gears 80, 82, 84 and 86.

Still referring to FIGS. 8-13, stated above, the gear train 25 alsoincludes a first sprocket 90 rotatably disposed on the intermediateshaft 70 and having a hub portion 90 a with a plurality ofradially-outwardly extending axial splines 91. A generally annularcoupler member 93 has a plurality of radially-inwardly extending splines93 a engaged with the first sprocket 90 and a plurality ofradially-outwardly extending splines 93 b engageable with the dog clutch96, as discussed below, to releasably connect or couple the sprocket 90with the shaft 70. A second sprocket 92 is fixedly disposed on theoutput shaft 28 and a flexible continuous element 94, preferably a chain95, is disposed about and driveably engages the first and secondsprockets 90, 92, respectively, such that the two sprockets 90, 92 (andthus the two shafts 70, 28) rotate in the same rotational direction A₂.With this structure, the input shaft 26 drives the output shaft 28 torotate in the second or “reverse” rotational direction A₂ in thefollowing manner.

As discussed above, the first gear 80 rotates at the input shaft speedS_(I) and rotatably drives the third gear 84 on the intermediate shaft70, causing the intermediate shaft 70 to rotate in the second angulardirection A₂ at the intermediate speed S_(I). Such rotation of theintermediate shaft 70 causes the first sprocket 90, when coupled withthe shaft 70, to rotatably drive the second sprocket 92 on the outputshaft 28. As such, the intermediate shaft 70 rotatably drives the outputshaft 28 in the second direction A₂ at a second or reverse output speedS_(R) as reduced by a sprocket reduction ratio R_(S). Preferably, thefirst and second sprockets 90, 92, respectively, each having workingdiameters relatively sized such that the output shaft 28 is driven inthe second or “reverse” rotational direction A₂ at a total gearreduction ratio G_(TR) of about seven point seven nine (7.79).

Preferably, mentioned above, the gear box 24 further includes agenerally annular dog clutch 96 disposed at least partially about thecoupler hub 74 of the intermediate shaft 70. The dog clutch 96 includesa plurality of radially-inwardly extending axial splines 97 engaged withthe hub splines 73, so as to rotatably couple the clutch 96 with theshaft 70, and is slidable in opposing directions along the intermediateshaft axis 71. The clutch 96 is engageable with the fourth spur gear 86when located at a first position with respect to the shaft 70 and isalternatively engageable with the coupler member 93, and thereby alsowith the first sprocket 90, when located at a second position withrespect to the shaft 70. More specifically, when the clutch 96 isdisposed in the first position, the clutch splines 97 engage the splines87 on the fourth gear hub portion 86 a so as to couple the dog clutch 96with the gear 86, thereby coupling the gear 86 with the intermediateshaft 70. Thus, when the dog clutch 96 is engaged with the fourth gear86, rotation of the input shaft 26 drives the output shaft 28 to rotatein the first, forward rotational direction A₁. Further, when the clutch96 is disposed in the second position, the clutch splines 97 engage theouter splines 93 b on the coupler member 93 so as to couple the dogclutch 96 with the sprocket 90, thereby coupling the first sprocket 90with the intermediate shaft 70. Thus, when the dog clutch 96 is engagedwith the first sprocket 90, rotation of the input shaft 26 drives theoutput shaft 28 to rotate in the second, reverse rotational directionA₂. In addition, the dog clutch 96 is also disposable in a third,intermediate position, located between the first and second positions,at which the clutch 96 is disengaged from or nonengaged with both thefourth gear 86 and the first sprocket 90, so as to provide a “neutral”setting of the power train 10. In other words, when the dog clutch 96 islocated in the third, intermediate position, the intermediate shaft 70is rotatable within the fourth gear 86 and the first sprocket 90 whilethe gear 86 and sprocket 90 remain generally stationary relative to theshaft 70, such that input shaft 26 will drive the intermediate shaft 70without driving the output shaft 28.

Referring to FIGS. 8-10, the gearbox 24 preferably also includes ashifter assembly 100 coupled with the dog clutch 96 and configured todisplace the dog clutch 96 between the first, third and second positionsas described above. The shifter assembly 100 includes a fork 102disposed within the housing interior chamber C_(H) and engaged with theclutch 96, a shift member 104 rotatably disposed within a side opening77 (FIG. 8) of the housing 60 and a crank lever 106 attached to theshift member 104. The fork 102 includes a base shaft portion 108 with aconnective peg 109 and a plate portion 110 attached to the shaft portion108. The plate portion 110 has an arcuate cutout 110 a sized to fitabout the dog clutch 96, specifically within an annular groove 98 in theclutch outer surface. Further, the shift member 104 includes anengagement tab 105 with a slotted opening 105 a and the fork peg 109 isdisposed within the opening 105 a, such that rotation of the shiftmember 104 causes the engagement tab 105 to push or pull the fork 102 inopposing directions generally along the intermediate shaft axis 71,thereby displacing the dog clutch 96 in like fashion. Furthermore, thecrank lever 106 is attached to an outer end 104 a of the shift member104 and is configured to rotate the shift member 104 within the sideopening 77. The crank lever 106 is coupled with a shift controller (notshown) in the vehicle operator station (i.e., the driver's area; notshown), such that a vehicle operator or “driver” may shift the powertrain 10 between the forward, neutral and reverse settings by operatingthe shift controller.

Referring now to FIGS. 2 and 3, the first and second propeller shafts14, 16 each basically includes an elongated, generally solid circularbar 120 and first and second connective members 122, 124, preferablyU-joints, each disposed at a separate end 120 a, 120 b, respectively, ofthe bar 120. Each bar 120 is rotatable about the shaft axis 15 or 17 ofthe particular propeller shaft 14, 16, respectively, and is configuredto transfer torque from the transmission output shaft 13 (i.e., gearboxshaft 28) to the associated axle 5, 6, the bar 120 of the frontpropeller shaft 14 preferably being sized so as to have a greater axiallength than the bar 120 of the rear propeller shaft 16. Further, eachfirst connective member 122 (only one shown) has a first portion 122 awith a plurality of internal, radially-inwardly extending axial splines(not shown) engaged with the radially-outwardly extending splines 68A,68B on the output shaft 28 so as to operably connect the propellershafts 14, 16 with the transmission 12. Further, the second connectivemember 124 of each propeller shaft 14, 16 is connected with a pinionshaft 141, 174 of the front and rear differentials 18, 20, respectively.

Referring to FIGS. 14-16, the front differential 18 basically includes,in addition to the gear member 30 discussed above, two side members130A, 130B each connected with a separate one of the two front axleshafts 7A, 7B and a carrier 132 releasably connectable with the gearmember 30 such that the first propeller shaft 14 rotatably drives thecarrier 132. The carrier 132 is configured to engage the side members130A, 130B with the gear member 30 when the side members 130A, 130Brotate at about the same speed as the gear member 30 and to disengagethe side members 130A, 130B from the gear member 30 when the members130A, 130B rotate at a greater speed than the gear member 30.Preferably, the carrier 132 is further configured to releasably connectwith each one of the two side members 130A, 130B when the two frontwheels 9A, 9B roll at about the same speed and to alternativelydisconnect from one of the two side members 130A, 130B when the frontwheel 9A or 9B connected with the one side member 130A, 130B,respectively, rolls at a greater speed than the other front wheel 9B,9A. With this structure, when the carrier 132 is connected with the twoside members 130A, 130B and is engaged with the gear member 30, eachfront axle shaft 7A and 7B receives about half of the torque transmittedto the gear member 30 from the first propeller shaft 14. Further, whenone of the two side members 130A or 130B is disconnected from thecarrier 132, the axle shaft 7B, 7A connected with the other side member130B, 130A receives generally all of the torque transmitted to the gearmember 30 from the first propeller shaft 14.

Preferably, the front differential 18 further includes a housing 134with a main body portion 135, two removable output cover plates 136A,136B and a removable input cover plate 137. The housing 134 has a rear,input opening 138 extending through the input plate 137 and two side,output openings 139A, 139B each extending through one of the outputplates 136A, 136B, the front axle axis 31 extending through the twooutput openings 139A, 139B. An input assembly 140 extends through theinput opening 138 and includes a shaft 141 connectable with the secondconnective member 124 of the first propeller shaft 14 and a pinion gear142. The pinion gear 142 is disposed within the housing 134 and isengageable with the gear member 30, such that the first propeller shaft14 drives the gear member 30, and thus the front axle shafts 7A, 7B,through the pinion gear 142. Preferably, the gear member 30 is a ringgear 144 and is preferably integrally formed with a generally tubularclutch housing 146. The clutch housing 146 has a central bore 148 sizedto receive the carrier 132 and a plurality of axially-extendingcontoured recesses 150 spaced circumferentially about the bore 148, eachrecess 150 providing a tapered cam surface 152, the purpose of which isdiscussed below. Further, each side member 130A, 130B is preferablyformed as a generally circular-cylindrical bar 154 having an outercircumferential surface 155 and an axial opening 156 with a plurality ofradially-inwardly extending axial splines 157. Each side member bar 154extends through and is rotatably disposed within a separate one of thehousing output openings 139A, 139B so as to be spaced apart along thefront axle axis 31. Each side member 130A, 130B is connected with aseparate one of the two front axle shafts 7A, 7B, respectively, byinserting a splined end 153 of each front axle shaft 7A, 7B within theaxial opening 156 of the particular side member bar 154. Preferably, oneof the two side member bars 154 has an axial peg 158 disposed within anaxial opening 156 of the other bar 154 so as to maintain axial alignmentof the two side members 130A, 130B during rotation of the front axleshafts 7A, 7B.

Furthermore, the carrier 132 preferably includes a generally tubularroll cage 160 having a two axially spaced sets of slotted openings 162A,162B, each set of openings 162A, 162B being spaced circumferentiallyabout the roll cage 160. The carrier 132 further includes two axiallyspaced sets of roll pins 164A, 164B, one pin 164A, 164B of each setbeing disposed within each one of the cage openings 162A, 162B,respectively. Each set of pins 164A, 164B is engageable with theproximal side member 130A, 130B, respectively, so as to operativelyconnect the carrier 132 with the particular side member 130A, 130B. Morespecifically, each pin 164A, 164B is partially disposed within one ofthe housing contoured recesses 150 and is contactable with the outercircumferential surface 155 of the associated side member 130A or 130B.When the axle shafts 7A, 7B rotate at a greater speed than the gearmember 30, the roll pins 164A, 164B all remain generally centered withinthe associated clutch housing contoured recesses 150, such that the sidemembers 130A, 130B rotate within the cage 160 while slipping past thepins 164A, 164B, as shown in FIG. 16A. As such, the axle shafts 7A, 7Bwill not be driven by or receive torque from the front propeller shaft14.

However, when the gear member 30 rotates at a greater speed than theaxle shafts 7A, 7B, such as when both rear wheels 9C, 9D slip relativethe base surface G, the clutch housing 146 displaces relative to theroll cage 160 until the roll pins 164A, 164B become wedged between thecam surface 152 and the outer surface 155 of the associated side memberbar 154, thereby coupling the side members 130A, 130B and the axleshafts 7A, 7B with the gear member 30, as shown in FIG. 16B. As such,the transmission output shaft 13 drives the front shafts 7A, 7B throughthe front propeller shaft 14, the pinion gear 142, the ring gear 144,the carrier 132 and the side members 130A, 130B. In addition, even whenthe side members 130A, 130B are coupled with the carrier 132, andthereby with the ring gear 166, one of the side members 130A or 130B maydisengage from the carrier 132 when the one front wheel 9A or 9B rotatesfaster than the other, such as when the vehicle 1 performs a turningmovement. Specifically, when the “outer” wheel 9A or 9B rotates at agreater speed than the “inner” wheel 9B, 9A, the side member 130A, 130Bconnected with the outer axle will start to rotate at a greater speedthan the roll cage 160, the clutch housing 146 and the ring gear 144,causing the roll pins 164A, 164B associated with the particular sidemember 130 to move toward the center of the housing contoured recesses150, enabling the particular side member bar 154 to slip past the rollpins 164A, 164B.

Preferably, the front differential 18 is provided by a commerciallyavailable differential device, most preferably a modified “CentralizedFront Drive Gearcase” from The Hilliard Corporation of Elmira, N.Y., asbasically described in U.S. Pat. No. 6,629,590 which is incorporated byreference herein. However, the front differential 18 may alternativelybe provided by any other appropriate differential device that enablesthe power train 10 of the present invention to function generally asdescribed herein.

Referring to FIGS. 2, 3 and 17-20, the rear differential 20 basicallyincludes, in addition to the gear member 32 discussed above, two sidemembers 170A, 170B and a carrier 172. The two side members 170A, 170Bare each connected with a separate one of the two rear axle shafts 8A,8B and the carrier 172 is releasably connectable with the gear member32, such that the second propeller shaft 16 rotatably drives the carrier172. The carrier 172 is configured to engage with the gear member 32when the carrier 172 rotates at about the same rotational speed as thegear member 32 and to disengage from the gear member 32 when the carrier172 rotates at a greater speed than the gear member 32. Preferably, thecarrier 172 is further configured to releasably connect with each one ofthe two side members 170A, 170B when the two rear wheels 9C, 9D roll atabout the same speed and to alternatively disconnect from one of the twoside members 170A or 170B when the rear wheel 9C, 9D connected with theside member 170A, 170B, respectively, rolls at a greater speed than theother rear wheel 9D, 9C. With this structure, when the carrier 172 isconnected with the two side members 170A, 170B and is engaged with thegear member 32, each rear axle shaft 8A and 8B receives about half ofthe torque transmitted to the gear member 32 from the second propellershaft 16. Further, when one of the two side members 170A or 170B isdisconnected from the carrier 172 and the carrier 172 is engaged withthe gear member 32, the axle shaft 8B, 8A connected with the other oneof the two side members 170B, 170A receives generally all of the torquetransmitted to the gear member 32 from the second propeller shaft 16.

Preferably, the rear differential 20 further includes housing 177 formedof upper and lower shell halves 178A, 178B and having a front, inputopening 179 and two side, output openings 180A, 180B, the rear axle axis33 extending through the openings 180A, 180B. An input assembly 169extends through the input opening 179 and includes a shaft 174connectable with the second connective member 124 of the secondpropeller shaft 16 and a pinion gear 176. The pinion gear 176 isdisposed within the housing 177 and is engageable with the gear member32, such that the second propeller shaft 16 drives the gear member 32,and thus the axle shafts 8A, 8B, through the pinion gear 176.Preferably, the gear member 32 is formed as a ring gear 178 having aninner contact face 178 a and the rear differential 20 includes a carrierhousing 180 connected with the gear 178 by a plurality of fasteners (notindicated). The carrier housing 180 bounds an interior chamber Cc andincludes an annular portion 179 disposable against the ring gear 178 andU-shaped portion 181. The housing U-shaped portion 181 provides aretainer wall 182 and has an axial opening 181 a extending through thewall 182 and two aligned radial openings 181 b (one shown), as bestshown in FIG. 18.

Referring particularly to FIG. 20, each side member 170A, 170B ispreferably formed as a relatively short circular tube 171 sized to fitwithin the carrier 172, as described below, and having an outercircumferential surface 173 and an inner circumferential surface forminga central bore 175. Each side member tube 171 has a plurality of axialsplines (not indicated) extending radially into the bore 175 andconfigured to engage with a splined end 167 a of a separate one of therear axle shafts 8A, 8B, so as to releasably couple the axle shafts 8A,8B with the gear member 32. Further, each tube 171 further has aplurality of radially-outwardly extending axial splines (not indicated)formed in the outer surface 173 and configured to engage with one clutchpack 186A or 186B of the carrier 172, as described below, so as tocouple the particular side member 170A or 170B with the carrier 172.Referring to FIGS. 17 and 20, each rear axle shaft 8A, 8B is preferablyformed as a circular bar 167 having a first splined end 167 a connectedwith the tube 171 of the associated side member 170A or 170B and anopposing splined end 167 b connected with a hub 183 of the associatedwheel 9A or 9B. Each axle shaft bar 167 is preferably rotatably disposedwithin a separate one of two tubular axle housings 193 fixedly attachedto the vehicle frame 2 (see FIG. 2).

Referring now to FIGS. 18-20, the carrier 172 preferably includes twogenerally circular cylindrical blocks 184A, 184B, each block 184A, 184Bhaving a central axial bore 185 with a counterbore section 185 a, andtwo clutch packs 186A, 186B each disposed within the counterbore section185 a of a separate one of the blocks 184A, 184B, respectively, andconfigured to engage with a separate one of the side members 170A, 170B,respectively. Each block 184A, 184B has an inner radial face 185 with apair of radially-extending, contoured recesses 187, the two block faces185 being generally facing and contactable with each other such that thetwo pairs of recesses 187 form a coupler opening 188 extending radiallythrough the carrier 172. Each carrier block 184A, 184B further has aplurality of axially extending, spring retainer openings 189 alignedwith corresponding openings 189 in the other block 184B, 184A. Thecarrier 172 further includes a plurality of springs 190 each disposedwithin each pair of aligned openings 189 and are arranged to bias thetwo carrier blocks 184A, 184B generally away from each other andgenerally toward the housing retainer wall 182 and the ring gear contactface 178 a, respectively, for reasons discussed below. The carrier 172is driveably connected with the carrier housing 180 by means of a pin192 extending through the two carrier housing coupler openings 182 a andthrough the carrier coupler opening 188.

Referring to FIGS. 20 and 21, each clutch pack 186A, 186B is configuredto releasably couple a separate one of the side members 170A, 170B,respectively, to the associated carrier block 184A, 184B, respectively,thereby operatively connecting the ring gear 178 with the associatedrear axle shaft 8A, 8B, respectively. Preferably, each clutch pack 186A,186B includes a plurality of annular reaction plates 194 connected withthe associated carrier block 184A, 184B and a plurality of annularfriction plates 196 connected with the associated side member 170A,170B, the plates 194, 196 being arranged in a staggered axial stackdisposed between inner and outer retainer rings 195, 197. In otherwords, the plates 194, 196 are spaced alternating in each pack 186A,186B such that at least a portion of each friction plate 196 is disposedbetween two of the reaction plates 194. Further, each annular plate 194,196 of the two clutch packs 186A, 186B has a central opening (noneindicated) sized such that the friction plates 196 fit about and aresplined to the outer surface 173 of the associated side member tube 171and the tube 171 extends through each reaction plate 194 with clearance.With the above-structure, when the springs 190 bias each block 184A,184B against the housing retainer wall 182 and the gear contact face 178a, respectively, each friction plate 196 is “sandwiched” between tworeaction plates 194 so as frictionally couple all the plates 194, 196 ofeach pack 186A, 186B and thereby operatively connect the side members170A, 170B with the carrier 172 (and thus the ring gear 178), asdiscussed in further detail below.

Generally, the clutch packs 186A, 186B couple the side members 170A,170B with the carrier 172 so that when the rear propeller shaft 16drives the ring gear 178 through the pinion gear 176, the ring gear 178rotatably drives the carrier housing 180, the carrier 172 and both sidemembers 170A, 170B, such that the two rear axles shafts 8A, 8B rotategenerally as a single unit about the rear axle shaft axis 33. However,when the vehicle 1 performs a turning movement, the “outer” axle shaft8A or 8B will experience a net increase in torque as the outer wheel 9Cor 9D attempts to rotate faster to negotiate the turn without slipping.Such increase in torque increases axial tension in the outer shaftsubassembly (i.e., axle shaft 8A or 8B, side member 170A or 170B, andcarrier block 184A or 184B), which compresses the springs 190 biasingthe particular carrier block 184A or 184B against the carrier housingwall 182 or the gear contact face 178 a, respectively. When the springs190 are compressed, the friction plates 196 are free to rotate relativeto the reaction plates 194, thereby permitting the particular sidemember 170A or 170B and connected axle shaft 8A, 8B to rotate at agreater speed than the carrier 172 (and thus the other, “inner” shaft 8Bor 8A) until the turning movement has been completed. At that point, thesprings 190 once again bias the particular carrier block 184A or 184Bagainst the housing wall 182 or the gear face 187 a and cause thefriction plates 196 to become again sandwiched between (and frictionallyengaged with) the reaction plates 194, such that the rear axle shaft 8Aor 8B is again rotatably coupled with the carrier 172 and the ring gear178 (and thus also the second propeller shaft 16).

Preferably, the carrier 172 and side members 170A, 170B are provided bya commercially available assembly, most preferably a “Detroit GearlessLocker” from Tractech Inc. of Warren, Mich. However, the carrier 172 andthe side members 170A, 170B may be provided by any other appropriatedevice(s) that function generally as described herein.

The power train 10 of the present invention, as described in detailabove, provides is clearly advantageous over previously known powertrains of utility vehicles. Most importantly, the number of controlsrequired to operate the utility vehicle 1 on any type of terrain withouta loss of traction are substantially reduced. Specifically, a vehicleoperator or “driver” generally operates the vehicle by operating asingle shift lever, i.e., to actuate the shifter assembly 100 betweenthe forward, reverse and neutral positions as discussed above, and willbe able to drive the vehicle through a range of speeds extending betweenzero (0) mph and at least twenty-five (25) mph and on any type ofterrain or traction conditions (i.e., “on-road” in dry, wet or snowyconditions, off-road on firm or muddy ground, etc).

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. For example, the transmission 12 of thepresent invention may be incorporated into a vehicle 1 that does notinclude a front differential 18 and/or rear differential 20 as eachdescribed herein, the power train 10 may include a gearbox and/ortransmission unit constructed in another appropriate manner, etc. It isunderstood, therefore, that this invention is not limited to theparticular embodiments disclosed, but it is intended to covermodifications within the spirit and scope of the present invention asdefined by the appended claims.

1. A power train for a vehicle, the vehicle having a frame, an enginemounted to the frame and having a rotatable engine output shaft, andfront and rear axles each rotatably connected with the frame, each axleincluding two axle shafts and two wheels, each wheel being connectedwith a separate one of the axle shafts and rollable upon a base surface,the power train comprising: a transmission operably connected with theengine and having a transmission output shaft; a first propeller shafthaving a first end, the first end being connected with the transmissionoutput shaft, and a second end; a front differential connected with eachone of the two front axle shafts and having a front differential gearmember configured to rotatably drive the two front axle shafts, thefront differential being operatively connected with the second end ofthe first propeller shaft such that the first propeller shaft drives thefront differential gear member at a first speed reduction ratio; asecond propeller shaft having a first end, the first end being connectedwith the transmission output shaft, and a second end; and a reardifferential connected with each one of the two rear axle shafts andhaving a rear differential gear member configured to rotatably drive thetwo rear axle shafts, the rear differential being operatively connectedwith the second end of the second propeller shaft such that the secondpropeller shaft drives the rear differential gear member at a secondspeed reduction ratio, the first speed reduction ratio being greaterthan the second speed reduction ratio such that the base surface drivesthe two front axle shafts to rotate independently of the frontdifferential gear member when at least one of the two rear wheels rollsupon the base surface, the rear differential being configured toreleasably connect each one of the two rear axle shafts with the otherone of the two rear axle shafts when each of the two rear wheels rollsat about the same speed as the other one of the two rear wheels suchthat the two rear axle shafts rotate generally as a single unit and toalternatively disconnect at least one of the two rear axle shafts fromthe other one of the two rear axle shafts when one of the two rearwheels rolls at a greater speed than the other one of the two rearwheels during a turning movement of the vehicle.
 2. The power train asrecited in claim 1 wherein each one of the first and second propellershafts is driven by the transmission output shaft so as to rotate atabout the same speed.
 3. The power train as recited in claim 1 whereinthe rear differential includes: two side members each connected with aseparate one of the two rear axle shafts; and a carrier connected withthe rear differential gear member such that second propeller shaftrotatably drives the carrier, the carrier being configured to releasablyconnect with each one of the two side members when the two rear wheelsroll at about the same speed and to alternatively disconnect from one ofthe two side members when the one rear wheel connected with the one sidemember rolls at a greater speed than the other rear wheel.
 4. The powertrain as recited in claim 3 wherein: when the carrier is connected withthe two side members, each rear axle shaft receives about half of thetorque transmitted to the rear differential gear member from the secondpropeller shaft; and when one of the two side members is disconnectedfrom the carrier, the rear axle shaft connected with the other one ofthe two carrier members receives generally all of the torque transmittedto the rear differential gear member from the second propeller shaft. 5.The power train as recited in claim 1 wherein the front differential isconfigured to: releasably connect each one of the two front axle shaftswith the front differential gear member when both of the rear wheelsslip with respect to the base surface and to alternatively disconnectthe two front axle shafts from the front differential gear member whenat least one rear wheel rolls upon the base surface; and releasablyconnect each one of the two front axle shafts with the other one of thetwo front axle shafts when each of the two front wheels rolls at aboutthe same speed as the other one of the two front wheels such that thetwo front axle shafts rotate generally as a single unit andalternatively disconnect at least one of the two front axle shafts fromthe other one of the two front axle shafts when one of the two frontwheels rolls at a greater speed than the other one of the two frontwheels during the turning movement of the vehicle.
 6. The power train asrecited in claim 5 wherein the front differential includes: two sidemembers each connected with a separate one of the two front axle shafts;and a carrier releasably connectable with the front differential gearmember such that the first propeller shaft rotatably drives the carrier,the carrier being configured to engage with the front differential gearmember when the carrier rotates at about the same rotational speed asthe front differential gear member and to disengage from the frontdifferential gear member when the carrier rotates at a greater speedthan the front differential gear member, the carrier being furtherconfigured to releasably connect with each one of the two side memberswhen the two front wheels roll at about the same speed and toalternatively disconnect from one of the two side members when the onefront wheel connected with the one side member rolls at a greater speedthan the other front wheel.
 7. The power train as recited in claim 6wherein: when the carrier is connected with the two side members andengaged with the front differential gear member, each front axle shaftreceives about half of the torque transmitted to the front differentialgear member from the first propeller shaft; and when one of the two sidemembers is disconnected from the carrier and the carrier is engaged withthe front differential gear member, the front axle shaft connected withthe other one of the two side members receives generally all of thetorque transmitted to the front differential gear member from the firstpropeller shaft.
 8. The power train as recited in claim 1 wherein thetransmission further includes: a gearbox including the transmissionoutput shaft and a rotatable gearbox input shaft operatively coupleablewith the transmission output shaft; and a continuously variabletransmission unit connected with the engine output shaft and with thegearbox input shaft such that the engine output shaft drives the gearboxinput shaft.
 9. The power train as recited in claim 8 wherein: thegearbox is configured such that the gearbox input shaft drives thetransmission output shaft at a single, fixed speed ratio in a firstrotational direction and alternatively drives the transmission outputshaft at a single, fixed speed ratio in a second, opposing rotationaldirection; the continuously variable transmission unit is configured sothat a ratio of a rotational speed of the engine output shaft to arotational speed of the gearbox input shaft is variable within a rangeof values having a lower limit of less than 1 and an upper limit ofgreater than
 3. 10. A power train for a vehicle, the vehicle having aframe, an engine mounted to the frame and having a rotatable engineoutput shaft, and front and rear axles each rotatably connected with theframe, each axle including two axle shafts and two wheels, each wheelbeing connected with a separate one of the axle shafts and rollable upona base surface, the power train comprising: a transmission operablyconnected with the engine and having a transmission output shaft; afirst propeller shaft having a first end and a second end, the first endbeing connected with the transmission output shaft such that thetransmission output shaft rotatably drives the first propeller shaft; afront differential connected with each one of the two front axle shaftsand having a front differential gear member configured to rotatablydrive the two front axle shafts, the front differential beingoperatively connected with the second end of the first propeller shaftsuch that the first propeller shaft drives the front differential gearmember at a first speed reduction ratio; a second propeller shaft havinga first end and a second end, the first end being connected with thetransmission output shaft such that the transmission output shaftrotatably drives the second propeller shaft so that each one the firstand second propeller shafts rotates at about a same speed as the otherone of the first and second propeller shafts; and a rear differentialconnected with each one of the two rear axle shafts and having a reardifferential gear member configured to rotatably drive the two rear axleshafts, the rear differential being operatively connected with thesecond end of the second propeller shaft such that the second propellershaft drives the rear differential gear member at a second speedreduction ratio, the first speed reduction ratio being greater than thesecond speed reduction ratio such that the base surface drives the twofront axle shafts to rotate independently of the front differential gearmember when at least one of the two rear wheels rolls upon the basesurface.
 11. A utility vehicle comprising: a frame; an engine mounted tothe frame and having a rotatable engine output shaft; front and rearaxles each rotatably connected with the frame, each axle including twoaxle shafts and two wheels, each wheel being connected with a separateone of the axle shafts and rollable upon a base surface; a transmissionoperably connected with the engine and having a transmission outputshaft; a first propeller shaft having a first end, the first end beingconnected with the transmission output shaft, and a second end; a frontdifferential connected with each one of the two front axle shafts andhaving a front differential gear member configured to rotatably drivethe two front axle shafts, the first differential being operativelyconnected with the second end of the first propeller shaft such that thefirst propeller shaft drives the front differential gear member at afirst speed reduction ratio; a second propeller shaft having a firstend, the first end being connected with the transmission output shaft,and a second end; and a rear differential connected with each one of thetwo rear axle shafts and having a rear differential gear memberconfigured to rotatably drive the two rear axle shafts, the reardifferential being operatively connected with the second end of thesecond propeller shaft such that the second propeller shaft drives therear differential gear member at a second speed reduction ratio, thefirst speed reduction ratio being greater than the second speedreduction ratio such that the base surface drives the two front axleshafts to rotate independently of the front differential gear memberwhen at least one of the two rear wheels rolls upon the base surface.